The invention relates to a quickly disintegrating pigment concentrate, in particular for coloring building materials such as concrete, as well as water-based paints and the like. The invention further relates to methods for coloring such materials with such pigment concentrates and the invention relates to the use of special cellulose products in such pigment concentrates.
The invention comprises a quickly disintegrating pigment concentrate which can be used for the coloring of building materials, like concrete, as well as for the coloring of water-based paints and the like. In particular the use of specific disintegration agents allows homogenous dispersion of the pigment in the material to be colored within very short mixing times and without the loss of color intensity. A further aspect of the invention is to keep the energy input needed for homogeneous dispersion of the pigment in the material, as small as possible to allow new and improved uses.
The subject matter of the invention is the use of a quickly disintegrating pigment concentrate for coloring dry mortar, cement-based building materials like ready-mixed concrete, roof tiles, and paving stones as well as the use of pigment concentrates for the coloring of paints, mulch, and paper, with the advantage, that the pigment concentrate begins to disintegrate immediately in the presence of water.
The invention further relates to dispersible filler products and like products, their use and the use of said cellulose products in such filler products.
The processing of pigments requires dispersion of the raw pigment material, with comminution of aggregates and agglomerates into pigment particles that fulfill the requirements for application in terms of particle size, in order to achieve optimal color development. This is true for inorganic pigments, which have been known for quite some time for the purpose of coloring building materials such as concrete and the like. However, pigments within the meaning of this invention can be any organic or inorganic pigments.
The common particle size of pigments is in the range of 0.01 μm to 0.9 μm. In commercially available products the pigments appear as agglomerates with a size of about 2-10 μm. Normally, the fraction remaining on a sieve with a mesh of 45 μm is 0.1% or less.
Typical granulates have a size of 200 to 1000 μm. In the final colored product, the pigment particles should again be present as single particles with a size of 0.01 to 0.9 μm.
If the coloration is to be even, the pigments or pigment concentrate should be added to the material to be colored, and dispersed therein homogenously while releasing the pigment particles. This is true for the coloring of dry materials as well as liquid ones. The solidified material contains the finely dispersed pigment particles and, thus, is homogenously colored throughout.
Important characteristics of the coloration to be achieved are color intensity and brilliance.
The properties of pigment concentrates are determined by requirements which are relevant to the different processing steps, from the formulation of the pigment product through intermediate products to the solid, colored material; however, all of them are interrelated and determine each other.
Thus, on the one hand, pure pigments would be preferred, due to their potential color intensity and brilliance of the coloration, because the pigment content is not diluted by additives. On the other hand, such powders behave poorly in processing, since they give off a lot of dust, tend to adhere to packing material, machinery parts and the like due to the fineness of their particles, and therefore, are hard to meter in the dosing equipment, due to blockage and bridging. Additionally, the flowability of pure pigment powders is insufficient.
When dispersing the pigments into the material to be colored, powders can also cause considerable problems, for example by forming pigment clumps (“nests”), which are not broken in the dispersing process and which become visible at the surface of the solidified, colored material. This is not only optically unfavorable (low development of color intensity, uneven coloration), but technically disadvantageous as well, because such pigment clumps do not have the required mechanical stability and can easily be eroded or washed out, which then results in open pores on the surface of the material and consequently leads to flaws in the surface of the finished material.
The need to apply high energy input to achieve homogenous dispersion of a pigment concentrate is not advantageous under various aspects. On the one hand, the use of mixing devices with high energy consumption is economically unfavorable; on the other hand, smaller building sites or manual operators often do not have intensive-mixing devices at their disposal, which renders therefore the incorporation of the pigment concentrate on site difficult or even impossible. A homogeneous coloration of the material without high mechanical energy application would for example, if used in dry mortar, facilitate and accelerate processing.
Similar considerations apply for other solid particles in building materials like fillers and the like, for concrete, mortar and cement. One example is calcium carbonate, which is used as a filler for concrete. Such solid components, like pigments, should be homogeneously dispersed as fast as possible and as effective as possible during mixing. The invention is suitable for such applications as well as for pigments. The following description, which refers to pigments, is applicable to such other solid components.
In order to avoid dust, improve metering and the overall flow properties, and to achieve a qualitative uniform color impression, it has been known in the prior art to process pigment particles and suitable additives, into pigment concentrates. For example, coated powder products, compacted products, and build-up or spray granulates are known.
A pigment concentrate according to the invention is a material, in which at least one additive (e.g., a dispersing agent, a wetting agent, a bonding agent) is added to the pigment particles by a processing step forming either powders or enlarged aggregates or shaped bodies (e.g. a granulate, a pellet, a tablet). In the invention, a preferred form of pigment concentrate is a granulate.
In the context of this description, “granulates” comprise materials with an average grain size that has been increased, with respect to that of the raw materials, by a processing step. Therefore, “granulates” not only comprise spray granulates and compacted granulates, but also, e.g., products resulting from a moisture treatment with subsequent curing and comminution, and products obtained by dry or essentially dry processing steps, e.g. dry produced granulates, briquettes and such like with subsequent comminution. Dry products within the meaning of the present invention have a residual moisture content of up to about 10 wt.-%
In principle, two contrary characteristics are required for pigment granulates or other shaped bodies, such as tablets. The granulates or other shaped bodies should be mechanically stable, and, simultaneously, ought to show good dispersing properties in the medium to be colored. The mechanical stability is responsible for good transportation characteristics, both for transport to the user, as well as for good metering and flow properties in the dosing equipment on site, due to a reduced dusting. This stability is provided by strong adhesive forces and depends, e.g., on the nature and the amount of the bonding agent, and on the pressure applied for shaping during the production of the concentrate. Dispersibility is influenced by the quality of milling prior to granulation (wet and dry milling), by the mechanical energy input in manufacture (e.g. line forces) and by dispersing agents, which reduce the adhesive forces of the dry granulate during the incorporation into a medium. Herein, the use of larger amounts of dispersing agents is limited by the additive/pigment cost ratio. Additionally, increased content of additives results in a respective reduction of the pigment concentration. By this, the use of additives is limited as well. Such additives and/or auxiliary agents should not disadvantageously modify the properties of the material to be colored. For example, regarding concrete it should be considered that the addition of certain water-soluble materials is regulated, so that the mechanical properties of the cemented concrete (e.g. firmness, pressure resistance) are not affected. Therefore, it is difficult to predict, and should be very carefully evaluated, whether the benefits of an additive outweigh the (possible) disadvantages.
Various processing methods for pigment granulates, such as spray granulation (spray drying over disks or jets), build-up granulation (mixers, fluid bed granulators, dishes, and/or drums), or extrusion or compacting processing have been described in the prior art:
It is known from DE-A1 29 08 202, to use aqueous carbon preparations (having a water content of 30% to 80%) in pearl granulates for coloring purposes in the cement industry. These techniques cannot be used for other pigments, and granulates having such water contents are generally disadvantageous, also for the use in building materials.
From DE-A1 29 40 156 it is known to granulate pigments together with bonding agents by spray granulation. The pigment granulates produced in this way are used for the production of colored ink, the coloration of plastics, paints, and the like. There is no reference to the coloration of building materials, and the like.
Color granulates containing more than 5% water by weight and up to 50% water by weight are known from EP-A2 0 191 278. According to this reference, granulates with a lower water content are not suitable for building materials.
In DE-A1 36 19 363, pigment granulates suitable, for the coloration of building materials comprising other pigments rather than carbon, have been described for the first time. According to this prior art, micro-granulates made from such pigments are produced by mixing them with bonding agents and subsequent spray drying. The bonding agents in question are essentially organic bonding agents, such as, e.g., lignin sulfonate. These granulates are commercially successful.
In DE-A1 39 18 694, micro-granulates without any organic bonding agents have been suggested. Here, inorganic compositions, in particular, oxides and/or hydroxides and corresponding hydrates are used as bonding agents. Such products are often problematic in practical use, because they tend to disperse incompletely during the incorporation into concrete and the like.
EP-A1 0 567 882 describes build-up, compacted and spray granulates having bonding agents, such as particularly mineral oil, wax, paraffin, and the like, for the purpose of coloring asphalt. In addition to bonding agents, the use of materials such as lignin sulfonate, molasses, starch, and the like should be possible. According to this disclosure, materials such as lignin sulfonate alone cannot be used as bonding agents.
From EP-A1 0 657 511 it is known to produce pigment granulates, with lactose as the bonding agent, by spray drying, with a residual moisture below 2.5% by weight.
Extrusion processes for the production of pigment granulates are known from U.S. Pat. No. 6,562,120 and US 2004 0040469.
For the use of coated powders, WO 97/29892 can be named as an example for the state of the art.
An example for a paste-like pigment concentrate is given in WO 01/55050. In such concentrates the pigment particles are pre-dispersed, which is generally advantageous. These products are however disadvantageous in view of their relatively high liquid content (water), which can cause increased transport costs, stability problems during storage (sedimentation), and often causes susceptibility to decomposition processes (biological affection, formation of mold) as well as legal complications regarding storage.
Therefore the concentrates according to the invention are preferably dry.
The combination of pigment particles, on the one hand, with auxiliary agents, on the other hand, for the production of pigment concentrates generally proceeds by means of moist and/or wet mixing procedures, but can also be effected by dry mixing procedures and, if necessary, with subsequent further processing to different product shapes. Subsequently, the products (herein also called “concentrates”) are not (any longer) present in the form of a mixed powder. The particles thus produced, comprising the pigment particles and at least one auxiliary agent, do not necessarily show a certain size. For example, they can be present as enlarged particles, which is typical for granulates; but they can also be processed by comminution methods, to achieve a fine particle concentrate. They include, for example, coated powders and shaped particles (e.g. granulate), more or less shaped by pressure or, if necessary, compacted, e.g. flakes or the like (including briquettes and other fairly big compacted bodies). In the technically most successful concentrates at present, they are homogeneous granulates, in particular spray granulates.
By using moist or wet mixing processes for the production of pigment concentrates, usability of the product can be affected.
On the one hand, the system of components for the production of the concentrate should be well mixable. This sometimes inhibits the utilization of auxiliary agents, which might otherwise be useful in later processing steps, for example, in combination with the materials to be colored. For example, if a liquid mixture for spray granulation is to be produced, the addition of the desired auxiliary agent to be added to the required concentrate should not excessively increase the viscosity of the mixture, because otherwise the mixing and spraying process is impeded and the concentrate cannot be produced with the required properties.
Additionally, the specific density of the concentrate as well as the relative ease, for water or other liquids, in penetrating the particles of the concentrate (granules), decisively influence the dispersibility.
To date, spray granulates provide the best combinations of properties in order to meet all requirements. Commercial products, such as, e.g., the GRANUFIN® products of the applicant contain, in addition to inorganic pigments (e.g., yellow, black, or red iron oxide pigment), dispersing agents and other auxiliary agents which promote the complete disintegration of the granules in the liquid material to be colored (e.g., liquid concrete.) These granulates are low dusting and resistant to breaking. They can easily be produced by means of spray drying and can be gravimetrically or volumetrically metered without dusting, for example, using automatic metering devices. They can easily be incorporated into the material to be colored, where they quickly disintegrate. Such products create homogenous coloring throughout, providing high color intensity and high brilliance.
These known spray granulates are suitable not only for concrete and similar building materials but also water-based coatings, paints as well as other materials to be homogenously colored throughout.
An important characteristic of pigment concentrates is the speed by which their particles disintegrate in contact with water (in particular when coloring a material), so that the pigment particles can be dispersed. In the coloring of building materials, such as concrete, as well as in paints, there is a strong demand for further reducing the mixing time necessary for homogenous coloration, because this reduces costs. Short mixing times for achieving homogeneous coloration as well as a reduction of the mechanical energy input during the blending process, would allow an improved application of the concentrate, for example, in dry mortar or ready-mixed concrete, e.g. for manual operators and at small building sites, where homogenous coloration should be achieved by manual mixing with water with a shovel, a manual mixer, or in a simple tumble mixer.
Mixing devices with low energy input and short mixing times, are also used for the production of paving stones, roof tiles and the like, so that also for such applications of the pigment concentrates, there are stringent requirements with respect to good dispersion properties.
For a long time, there has been a strong demand for pigment concentrates, whose particles, when used appropriately, disintegrate as quickly as possible when contacting the material to be colored, preferably disintegrating immediately and in such a way that the pigment particles to be dispersed are thereby essentially released.
It has been shown that the state of the art can be improved. The use of pigment concentrates according to the invention allows a homogeneous coloring of building material with very short mixing times and without applying high energy input to achieve dispersion. The use of organic disintegration agents is particularly advantageous.
In spite of the fact that previously, for example in DE 197 31 698 it has been suggested to add, among other things, disintegrating agents to the compacted granules, this suggestion has not been successful, because as of today no product is available containing such agents.
This is probably caused by the fact that the known disintegrating agents have been developed for the use in pharmaceutical applications, particularly for the quick disintegration of tablets. An auxiliary agent that can be used without problems under physiological conditions is not necessarily suitable under entirely different conditions, for example, for the production and application of spray granulates.
For example, DE 197 31 698 discloses particularly strongly hydrophilic polymers with a correspondingly large absorption capacity for water as disintegration agent, such as cellulose derivatives, dextrans, and cross-linked polyvinyl pyrrolidone (cPVP).
Most of the strongly hydrophilic cellulose derivatives are water soluble derivates with additional hydrophilic substituents, known, for example, as glues, thickening agents, and the like. Although the disintegrative effect of such cellulose derivates is considerable, other problems occur in their use, particularly because they increase the viscosity of the liquid pigment mixture prior to spray drying to such an extent that the spray drying is impeded. When used with concrete, water-soluble cellulose derivates can lead to increased blooming, which is, of course, extremely undesired. Furthermore, they increase the amount of (only very limitedly acceptable) water-soluble components and also affect the setting properties of the corresponding colored products.
Dextrans form very hard granulates; instead of a disintegrative effect, the additive causes the opposite, namely a noticeable deceleration in the disintegration of the granulate, caused by too strong adherence. Additionally, granulates produced with dextrans show a more or less marked color shift (blue shift) caused by insufficient disintegration.
The application of cross-linked PVP as a disintegrative agent in spray and compacted granulates is also less favourable.
Similar problems result from the majority of the other disintegrating agents known from prior art.
Based on this, an object of the invention is to disclose pigment concentrates, allowing a quicker dispersion than the known concentrates, while retaining at least essentially the advantages of such concentrates. Another object of the invention is to disclose such pigment concentrates, that sufficiently disintegrate during their intended use, requiring only little mechanical energy input.
Another object of the invention is to suggest respective coloring processes for materials, which were before colored according to the prior art, using the type of pigment concentrates mentioned here.
A further object of the invention is to provide an improved pigment concentrate for the coloring of building materials like for example dry mortar, ready-mixed concrete, and paving stones as well as for papers and organic materials, like mulch, where homogenous mixing without the application of high energy input is advantageous.
Last but not least, an object of the invention is the use of certain celluloses as disintegrating agents in concentrates according to the invention.
The combinations of features defined in the independent claims serve to attain one or more of these objects, in whole or in part.